AU722134B2 - Regenerator heat exchanger having one or more adjustable performance characteristics - Google Patents

Description

Regenerator Heat Exchanger Having One of More Adjustable Performance Characteristics CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of pending application U.S. Ser. No. 08/132,523, filed Oct. 6, 1993 (Attorney Docket No. AIR-8).

I Field of Invention 2 The present invention relates generally to rotary energy exchange devices, and, 3 more particularly, to rotary energy exchange wheels having an energy transfer matrix 4 comprised of a plurality of readily removable, interchangeable segments. The interchangeable segments comprising the energy transfer matrix can be made with 6 different values of at least one performance characteristic so that by assembling the 7 matrix with segments of more than one value, or substituting one or more select 8 segments of one value for segments of a different value, the total performance *9 characteristic of the entire matrix of the energy transfer wheel can be adjusted at any time, whether at the time of or subsequent to its manufacture and before or after 11 installation and use.

12 13 Backgrund of the Invention 14 Regenerator heat exchange devices or regenerators are well known. One type of regenerator is the rotary air-to-air heat exchanger, which is typically in the form of 16 a rotary heat exchange wheel including a matrix of heat exchange material. For 17 example, see Canadian Patent No. 1,200,237 (Hoagland) and U.S. Patent Nos.

:18 4,432,409 (Steele) and 4,875,520 (Steele et all assigned to the present assignee 19 (and hereinafter the U.S. Patents being referred to as the '409 and '520 Patents, respectively) and incorporated herein by reference. Rotary air-to-air hieat exchangers 21 transfer .sensible heat -and moisture, usually between ducted and counterfiowing 22 airstreams, for the purpose of conserving energy within a building, while providing 23 outdoor air ventilation to remove air pollutants from buildings. For example, Leat and 24 moisture from indoor air being exhausted to the outdoors during the heating season are transferred to the cooler, dryer incoming fresh air, and during the cooling season, heat -26 and moisture from entering warm moist outdoor air is transferred to the cooler drier S 27 air as it is exhausted to the outdoors. Transfer of heat and moisture in this manner can 1 typically reduce the amount of energy required to heat, cool, humidify or dehumidify 2 the incoming ventilation air typically anywhere between about 50% and about 85 3 depending primarily on the performance characteristics of the rotary energy transfer 4 wheel.

It is well known to make such rotary heat exchange wheels with a matrix of 6 heat exchange material (capable of absorbing sensible heat) coated with a desiccant 7 material (capable of absorbing moisture and thus latent as well as sensible heat). Such 8 regenerators are used in heating and/or air conditioning systems in which the transfer 9 of both sensible and latent heat is desired in the ventilation portion of such systems.

as, for example, in the case of air conditioning systems used in summer climates 11 characterized by hot and humid outdoor air. In such climates, it is often desirable to 12 bring fresh air in from the outdoors. In this case the regenerators are used to transfer 13 sensible and latent heat from incoming air to the outgoing air. The removal of latent 14 heat from incoming air prior to passing the air over evaporation coils of an air 15 conditioning system helps reduce the heat load imposed on the air conditioning system.

9*o) 16 To achieve maximum latent heat transfer, as is well known in the prior art, a 17 suitable sensible heat exchange matrix material such as plastic high molecular 18 weight, synthetic polymers), aluminum, or Kraft or other fibrous paper is completely 19 and uniformly coated with a desiccant material in accordance with processes known to those skilled in the art. In one type of regenerator, the matrix comprises a plastic 21 strip coated with a desiccant material wound around a hub so as to form a heat 22 exchange wheel. The airflow through the wheel, and the efficiency of heat transfer 23 by the wheel matrix, are determined in part by the spacing between opposing surfaces 24 of adjacent portions of the strips of the matrix. This spacing can be controlled by controlling the height of embossments in the strip. For a given air flow, the tighter 26 the spacing (or the denser the wrap), the higher the efficiency of heat exchange matrix 27 and the greater the pressure drop across the two sides of the wheel. See U.S. Patent 28 Nos. 4,432,409 to Steele and 4,825,936 to Hoagland et al. Thus, the rated air flow 29 and efficiency through a regenerator wheel of a given diameter are performance characteristics of the regenerator matrix that are in part determined by the wrap 31 density of the strips Minimum amounts of outdoor air ventilation for control of WO 98/19763 PCT/US97/20333 1 indoor air pollution are now frequently specified by ventilation building codes and 2 standards in terms of cubic feet of air per minute/per occupant (CFM per person), but 3 for a particular space this number may typically vary by a factor of up to four based 4 upon the nature of the occupancy and the anticipated occupant density, schools, office buildings, libraries, restaurants, etc. Typically, ventilation systems are designed 6 and installed in buildings to meet the initial intended occupancy requirements. For 7 reasons of economy, ventilation systems will also generally be manufactured and 8 installed to only provide minimum required ventilation rates to a building. Such 9 systems may include variable speed blowers and adjustable air dampers to allow for changes of ventilation air in the event of a change of occupancy that requires higher 11 ventilation rates. For ventilation systems including porous heat exchange, energy 12 transfer regenerator wheels, the amount of additional ventilation that can be provided 13 in this manner is, however, partly restricted by the pressure drop across the wheel 14 through which supply and exhaust air must flow. With the pressure drop across the energy transfer wheel increasing in direct proportion to the increase of airflow, the 16 maximum pumping capacity of a variable speed blower can be reached before the 17 desired increase of airflow is obtained.

18 Further, under some circumstances maximum latent heat transfer may not be 19 desirable. For example, under moderate winter conditions it is often desired to use a ventilation system including a sensible heat exchange matrix wheel to remove 21 substantial amounts of moisture from a building. However, when the outdoor air 22 becomes very cold and dry the moisture removal rate provided by a sensible heat 23 exchange matrix wheel may become excessive, and the indoor air humidity may 24 become uncomfortably low. In this case it becomes desirable to have some desiccant coating present on the heat exchange matrix so as to increase moisture retention (and 26 thus allow additional moisture in the air being exhausted from the building to be 27 transferred to the incoming fresh air), but a fully desiccant coated wheel may retain 28 excessive amounts of moisture so that an excessive amount of moisture is returned to 29 the interior of the building with the incoming fresh air.

Such moisture control problems, thus, are not necessarily solved by 31 substituting a latent heat exchange matrix wheel wheels heretofore only available WO 98/19763 PCT/US97/20333 1 with a matrix having a uniform coating of desiccant material) for a sensible heat 2 exchange matrix wheel a wheel having a matrix made entirely of sensible heat 3 exchange materials). Whereas a fully desiccant-coated matrix wheel may retain 4 excessive amounts of moisture, a sensible matrix wheel without a desiccant coating material recovers only moisture which condenses on the matrix when the dew point 6 of the airstream is above the temperature of the surface of the matrix. The condensed 7 moisture is reevaporated back into the warmer and drier counterflowing airstream 8 passing through the matrix. This small amount of moisture recovery by a sensible heat 9 exchange matrix may be insufficient to maintain the desired indoor humidity.

The latent heat exchange efficiency desired of a heat exchange matrix also may 11 vary according to changes in the usage of the building it services. For example, the 12 moisture removal rates desired in a retail space may differ from that desired in the 13 same space later converted to a restaurant. Furthermore, in some situations, the 14 desired latent heat exchange efficiency may not be fully determinable until the regenerator is tested at the building itself. Under such circumstances, it is possible 16 that neither regenerators made entirely of heat exchange materials uniformly coated 17 with desiccant material, nor regenerators made entirely of sensible heat exchange 18 materials (not coated with desiccant material) provides the desired latent heat exchange 19 efficiencies since regenerators of both types are usually offered in only a limited number of values of efficiency.

21 Moreover, after the system is installed the volumetric air flow requirements 22 may change, because of a change of use or occupancy. More specifically, ventilation 23 systems are usually designed to provide a predetermined volumetric air flow so as to 24 meet specific building code and use requirements. If the system including the blower and heat regenerator wheel are originally designed for one range of air flows, and the 26 changes require a different range of air flows, adjustments must be made. Typically, 27 due to the costs of installing ventilation systems in large buildings, such changes in the 28 ventilation system after they are installed are not readily accomplished. For example, 29 the volumetric rate of air flow can be adjusted by only a small amount by changing the pulley systems of the blower. One could also change the entire regenerator matrix 31 wheel with one of a different wrap density. Thus, following installation of a WO 98/ 1 2 3 4 6 7 19763 PCTIUS97/20333 ventilation system, it may be necessary to adjust the flow rate and/or other performance characteristics of the regenerator matrix wheels in response to changes in building design or usage.

Thus, it would be advantageous to be able to customize or adjust in an economical way the airflow rates, customize or adjust the latent and sensible heat transfer characteristics of the regenerator wheel, or customize or adjust some other performance characteristic during or after its manufacture or at the installed site.

Obiects of the Invention An object of the invention is to provide a rotary heat regenerator with one or more performance characteristics that are adjustable.

Another object of the invention is to-provide a rotary heat regenerator wheel having performance characteristics, including latent and sensible heat transfer efficiencies, air flow rate, and pressure drop, which can be readily adjusted after manufacture or installation to meet changing ventilation requirements.

Summary of the Invention The above and other objects of the invention are achieved, at least in part, by providing a rotary heat regenerator having a heat exchange matrix with one or more performance characteristics which can be customized or adjusted during or after manufacture, or in the field. Preferably, the matrix of the regenerator wheel includes a plurality of interchangeable, removable sections or segments so that any or all of the segments can be replaced at any time with other like sized segments which differ with respect to at least one performance characteristic. The performance characteristic can be latent and sensible heat transfer efficiencies, or air flow rate and pressure drop. Air flow rate and pressure drop are related to the surface area density (defined below) of the matrix used in the regenerator. Thus, in one embodiment, the performance characteristic is determined by the latent heat transfer characteristic, while in another embodiment the performance characteristic is determined by the surface area density.

In the first embodiment, at least one of the segments is made of a heat WO 98/ 1 2 3 4 6 7 8 9 11 12 13 14 16 17 18 19 21 22 23 24 26 27 28 29 31 '19763 PCT/US97/20333 exchange matrix material coated with a desiccant material, while at least one other segment is not coated and is primarily used to transfer sensible heat. Thus, through the incorporation of both desiccant-coated and uncoated heat exchange segments into an energy transfer wheel in adjustable proportions, the customized rotary heat regenerator matrix is able to transfer latent heat with an efficiency between that of purely sensible heat exchange matrices and matrices made entirely of heat exchange materials uniformly coated with a desiccant. In accordance with this aspect of the invention, through division of the matrix into removable segments together providing a combination of desiccant-coated and uncoated heat exchange material, the present rotary heat regenerator is further able to transfer latent heat with an efficiency which can be adjusted at any time, whether during or following the manufacturing stage, or on-site during installation, or after operating experience or building usage changes necessitate changes in these performance characteristics.

With respect to the second embodiment, the performance characteristic herein referred to as the "surface area density" (the ratio of the surface area to which the air is exposed as the air passes through the heat exchange matrix to the cubic volume of air space within the matrix between the various heat exchange surfaces, or surface(ft 2 )/volume(ft)) of the regenerator wheel is customizable or adjustable in order to adjust the ratio of volumetric airflow rate to pressure drop. Such changes in surface area density affect the energy transfer efficiency so a tradeoff is made between efficiency and air flow capacity for a given wheel diameter. This ratio can be adjusted by varying the spacing between adjacent layers of heat exchange surfaces within the material, or the surface area to which the volume of air passes. More specifically, decreasing the spacing through which a fixed volume of air passes, or increasing the surface area to which the fixed volume of air is exposed will increase this ratio, and vice versa. For example, the wheel comprises a matrix comprising a plurality of segments each including a stack or multiple layers of strips of heat exchange material (coated or uncoated). Some of the strips can be provided with embossments on one or both sides which keep adjacent strips spaced from one another and thus provide spaces for airflow through the matrix. The height of the embossments can be selected to provide greater or lesser spacing between adjacent WO 98/19763 PCT/US97/20333 1 strips in the matrix, thereby establishing a desired surface area density of the matrix.

2 In accordance with this embodiment of the invention, the heat exchange matrix can be 3 customized by using a plurality of segments in which at least two segments are Of 4 different surface area densities, regardless of whether they are coated with a desiccant material or not. For example, the desired surface area density of the entire matrix 6 already made of a plurality of segments having the same surface area density can be 7 modified by substituting at least one segment having a higher or lower surface density 8 with a corresponding segment in the matrix.

9 Still other objects and advantages of the present invention will become readily apparent to those skilled in this art from the following detailed description wherein a 11 preferred embodiment is shown and described, simply by way of illustration of the 12 best mode of the invention. As will be realized, the invention is capable of other and 13 different embodiments, and its several details are capable of modifications in various 14 respects, all without departing from the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not restrictive.

16 17 Brief Description of the Drawings 18 For a fuller understanding of the nature and objects of the present invention, 19 reference should be had to the following drawings, wherein: Fig. 1 is a graph of the relationship between heat transfer efficiency and the 21 surface available for heat transfer; 22 Fig. 2 is a front view of a preferred embodiment of a rotary heat exchange 23 wheel, positioned within a rotary heat exchange system, the wheel comprising a matrix 24 made with removable segments in accordance with the present invention; Fig. 3 is a cross-sectional view taken of a portion of the matrix along line A-A 26 shown in Fig. 2, and comprising both strips of desiccant-coated material; 27 Fig. 4 is a cross-sectional view taken of a portion of the matrix along line A-A 28 shown in Fig. 2, and comprising an alternative to that shown in Fig. 3 both 29 strips of uncoated sensible material); Fig. 5 is a perspective view of a part of the wheel of Fig. 1 with sections 31 removed; and WO 98/19763 PCT/US97/20333 1 Fig. 6 is a perspective view of one of the sections used in the Fig. 1 2 embodiment.

3 4 Detailed Description of the Drawings In accordance with the present invention, a rotary heat regenerator, preferably 6 in the form of a rotary air-to-air heat exchange wheel, comprises a heat exchange 7 matrix formed from a plurality of interchangeable, removable segments. The matrix 8 can be assembled so that at least two of the segments are different from one another 9 with respect to a predetermined performance characteristic, such as latent heat exchange transfer characteristic or air flow rate, so that the performance characteristic 11 of the matrix can be established during manufacture, or adjusted after manufacture and 12 installation and/or use in the field by substituting different segments in predetermined 13 numbers and arrangement.

14 The invention is based in part upon the realization that it may be desirable to adjust the ventilation rate of a ventilation system utilizing a porous regenerator heat 16 exchange matrix, beyond the limits imposed by the pressure drop across the 17 regenerator device, or modify the latent heat transfer efficiency between those 18 provided by regenerator devices comprising a matrix solely made of a sensible heat 19 exchange material and regenerator devices comprising a matrix solely made of a heat exchange material uniformly coated with a desiccant, without developing new coating 21 methods, by utilizing both types of materials in the same regenerator in a proportion 22 directly related to the desired latent heat transfer efficiency.

23 The desiccant-coated, latent heat exchange matrix materials provide surface 24 area for moisture transfer. As stated above, moisture that can be recovered by sensible heat exchange material (without a desiccant coating material) matrix is that 26 which condenses on the material when the dew point of the airstream is above the 27 temperature of the surface of the material. For purposes herein such a matrix material 28 is referred to herein as a "sensible heat exchange material" and is used primarily to 29 transfer sensible heat. A "latent heat exchange material", however, includes a desiccant that is used for transferring at least latent heat (associated with moisture) and 31 is capable of also transferring sensible heat. Thus, the latter term includes enthalpy WO 98.

1 2 3 4 6 7 8 9 11 12 13 14 16 17 18 19 21 22 23 24 26 27 28 29 31 /19763 PCTfUS97/20333 exchangers. Moisture transfer efficiency, like sensible heat transfer efficiency, varies as a function of the available transfer surface area. The relationship, as shown graphically in Fig. 1, is not linear, but exponential. At low efficiencies, near zero percent, doubling the surface transfer area will essentially double the efficiency; at higher efficiencies, near 100%, doubling the surface transfer area will result in very small efficiency increases, approximately 1% or At around 80% to 85 efficiency, a common operating point for regenerator matrices made of plastic heat exchange materials, doubling the surface transfer area will result in an efficiency increase of around 8% to 10%, from approximately 70% to 80% or from approximately 80% to 88%. Accordingly, we have found that a regenerator matrix made of 50% plastic sensible heat exchange material and 50% latent desiccant-coated plastic heat exchange material will have approximately the same sensible heat transfer efficiency of the regenerator matrix made of 100% sensible heat exchange material, but only approximately 70%-80% of the moisture transfer efficiency of the regenerator matrix made of 100% desiccant-coated heat exchange material (depending on the position along the curve of Fig. A regenerator matrix with these efficiencies will provide suitable sensible heat recovery, and often a much more suitable moisture recovery, compared to regenerator matrices made of entirely latent, desiccant-coated material or of entirely sensible heat exchange material. Furthermore, in accordance with the present invention, regenerator matrices can be modified or changed after manufacture, and even at an installation site to provide various other sensible heat and moisture transfer efficiency combinations for other climatic conditions and different building uses by substituting matrix segments made of different amounts of latent and sensible heat exchange materials.

In one preferred embodiment, generally shown in Fig. 2, and described in greater detail hereinafter in connection with Figs. 4-6, the plastic matrix comprises a plurality of separate wedge-shaped matrix elements or segments each formed, for example, by cutting completely through one or more strips which are wound into a wheel and subsequently cut, for example, with a heated tool from one face to the opposite face so that the resulting wedge-shaped elements each have arc-shaped strips fused at their ends along the cut line. Matrix segments can be formed from strips of WO 98/19763 PCT/US97/20333 1 plastic high molecular weight, synthetic polymers), aluminum, Kraft or other 2 fibrous paper, or steel. Plastic of a type capable of being heat sealed is preferably 3 used. Those skilled in the art will recognize that other matrix construction techniques 4 may be employed, and matrices of other configurations, such as those containing flat layers, or a honeycomb structure, may be produced. As described in greater detail 6 hereinafter in connection with Figs. 3 and 4 and in the '237, '409, and '520 Patents, 7 suitable spacing means are provided in the matrix so as to form gas passageways in an 8 axial direction through the wheel segments at a given surface area density.

9 In the matrix of Fig. 2, the heat exchange material 16 of each segment consists of strips made either of a sensible heat exchange material or a latent heat exchange 11 material spirally wound together before being cut into the individual segments and 12 subsequently attached to the hub 12. The strips of latent heat exchange material are 13 coated with a desiccant as illustrated more fully in Fig. 3, whereas the strips of 14 sensible heat exchange material are not as illustrated more fully in Fig. 4.

Referring to Figs. 3 and 4, two examples of arrangements for the plastic strips 16 of two different segments are illustrated in Figs. 3 and 4, wherein the matrix of one 17 segment is formed with two alternating types of strips made of a plastic sensible heat 18 exchange material coated with a desiccant material, and one segment formed with two 19 alternating types of strips made of an uncoated plastic sensible heat exchange material.

In both arrangements, the means for forming spaces between adjacent strips includes 21 regularly distributed protrusions or embossments 30 formed on one of the two strips 22 used to form the matrix of the segment, while the other strip is flat. The embossments 23 30 extend in both directions from the surfaces of embossed strip 32a so as to separate 24 the embossed strip 32a from the adjacent surfaces of the flat strip 32b and thus form air channels 36 for the flow of air axially through the matrix 10. The height of the 26 embossments determines the extent of separation between adjacent strips and thus 27 determines the flow passage hydraulic diameter, the surface area density, and thus the 28 air flow versus pressure drop relationship, for the matrix.

29 In Fig. 3, the embossed strip 32a and flat strip 32b are coated, preferably on both surfaces, with desiccant material 40 (shown in greatly enlarged detail) so as to 31 provide two strips of latent heat exchange material. A dry desiccant, such as silica WO 98/ 1 2 3 4 6 7 8 9 11 12 13 14 16 17 18 19 21 22 23 24 26 27 28 29 31 19763 PCT/US97/20333 gel, is preferably used. A preferable method of uniformly coating plastic strips with dry desiccant is described in the '520 Patent. In Fig. 4, the matrix is identical to that shown in Fig. 3, except that the embossed strip 32a and flat strip 32b are both made of an uncoated sensible heat exchange material. If desired, the matrix can include strips of both latent heat exchange material desiccant-coated) and sensible heat exchange material uncoated).

In addition, the surface area density of a segment is in part determined by the height of the embossments 30, so that segments of different surface area densities can be provided by making the segments with embossed strips 32a having embossments of differing heights. Clearly, increasing the height of the embossments reduces the surface area density of a segment, and vice versa.

Thus, as described with reference to Figs. 3 and 4, each matrix segment can be formed with all the surface area providing latent heat transfer; sensible heat transfer only, or a combination of both. Segments of varying surface area densities easily can be provided by providing the embossed strips 32a of the segments with embossments of one being of a different height from those of another, or all segments can have the same surface area density but vary with respect to some other performance characteristic. The latent heat transfer efficiency of the matrix is determined by a curve similar to that shown in Fig. 1. When both coated and uncoated surfaces are used in the same segment, the ratio of the two can be adjusted, in one embodiment, by adjusting the amount of surface area that is provided by latent heat transfer material relative to the surface area that is provided by the sensible heat transfer material only. For example, when making a particular segment by using three strips coated with the desiccant and one strip of uncoated sensible heat exchange material the ratio of approximately 3 to 1 of relative surface area is achieved with a corresponding latent heat transfer efficiency as determined by the curve of the type shown in Fig. 1. With this arrangement, wheels of different ratios of coated and uncoated surface areas can be provided so that a particular wheel segment can be selected at the site where the rotary heat exchange regenerator is installed so as to select a desired latent heat transfer efficiency.

As shown in Figs. 2, 5 and 6, the embodiment shown is particularly adapted WO 98 1 2 3 4 6 7 8 9 11 12 13 14 16 17 18 19 21 22 23 24 26 27 28 29 31 /19763 PCTUS97/20333 for commercial use, in which wheels tend to be of larger dimensions, although the principles can be applied to smaller, residential wheels. In the embodiment shown the matrix 10 is divided into a plurality of removable wedge-shaped elements 50 of heat exchange material. A selected number of elements 50a are made of a latent heat exchange material; the remaining elements 50b are made of a sensible heat exchange material. The proportion of elements which are desiccant-coated and elements which are nondesiccant-coated can be varied according to the latent heat transfer efficiency desired. In addition, segments of different surface area densities can be used to form the matrix of a wheel. In this instance where eight elements are used, each circumscribing 450 of the wheel, nine different latent heat exchange efficiencies and almost an infinite number of different pressure drops can be provided at the site where the wheel is used, by using anywhere from zero to eight elements made of latent heat exchange material, and segments of different surface area densities. If desired each segment can comprise some layers of sensible heat exchange material, and some layers of latent heat exchange material, so that the possible combinations of the percentage of sensible heat exchange material and the percentage of latent heat exchange material used to comprise the matrix are almost limitless.

Referring more specifically to Figs. 5 and 6, the wedge-shaped elements 50 of heat exchange material are preferably made from wheels of spirally wound plastic strips as described previously or by any other suitable method. For each type of element 50a, 50b, wheels wound from two or more strips with suitable spacing means, such as embossments 30, are preferably used so as to form layers with channels for the flow of air. The number of segments having different surface area densities is a matter of choice.

The sections can be supported in any suitable manner, and are preferably supported so that each section may be individually removed and replaced with other segments. For example, they can in a suitable frame so that each can be easily mounted and replaced at the site where the wheel is used. A frame, for example, is shown in Figs. 5 and 6, and comprises wedge-shaped openings for supporting the respective wedge-shaped elements 50. The wheel includes a matrix hub 52 comprising two circular disks 51 and 53, the hub being provided with a shaft 54 so that the wheel WO 98/19763 PCT/US97/20333 1 can be rotatably mounted within a rotary exchange device. The wheel also includes 2 a plurality of spokes 56 extending radially from and supported at one end by the hub, 3 and supported at the other end by an outer band 58. Means, such as plastic foam 4 strips 60, are provided on each side of each spoke for providing an airtight seal between each element 50 and each spoke 56. Means are also provided for removably 6 securing each of the elements 50 in the frame. The latter means, for example, 7 includes a retaining tab 61 provided on one side of the wheel at the place where the 8 spoke connects to the outer band 58 so as to provide a retaining element for each 9 element 50 when it is positioned in the wedge-shaped opening. A spring clip 62 is attached to the outer end of each spoke. Spring clip 62 is adapted to be compressed 11 by the wedge-shaped element 50 when the latter is inserted in the respective opening 12 so as to secure the wedge-shaped element in place. The spring clip includes a 13 rectangular stop 64. Once in place each wedge is locked in place by a retainer tab 66, 14 which is attached to one end of a spring retainer strap 68, the other end of the strap being attached to the outer surface of the outer band 58 so that the tab 66 extends 16 through a slot 72 in the outer band into contact with the wedge. A grip 70 is provided 17 on the strap for allowing the user to pull back on the strap so that the tab will pull out 18 of contact with the segment 50 and from the slot 72, making it possible to pull the 19 segment 50 out of the wedge-shaped opening.

As shown in Fig. 6, each of the wedge shaped elements 50 is provided, for 21 example, with a segment hub retainer attachment 74, adapted to engage hub 52 22 between the disks 51 and 53 so as to prevent any damage to the element 50 when 23 inserting or removing the element. The spring clips 62 urge the wedge-shaped 24 elements 50 toward the hub 52 so as to be sandwiched between the hub's axially opposing disks 51 and 53.

26 Thus, to allow removal or insertion of one of the wedge-shaped elements 27 the associated grip 70 of the spring retainer strap is pulled until the retainer tab 66 is 28 drawn back through the slot 72 of the outer band 58 away from the hub 52. When the 29 grip 70 is released, the tab 66 snaps radially inward through the slot 72 so as to prevent the wedge shaped element 50 from moving.

31 The use of removable wedge-shaped elements has a further advantage for WO 98/19763 PCTfUS97/20333 1 commercial rotary heat regenerators, which are generally larger in size than residential 2 rotary heat regenerators. When the matrix segments must be removed (for 3 substitution, testing, replacement, cleaning, etc.), the less bulky elements are easier 4 to handle than a whole, undivided matrix. It should also be appreciated by those skilled in the art that a divided matrix of multiple removable segments can be used for 6 lower airflow residential applications within the scope of the present invention.

7 A standard wrap density of matrix material in currently available regenerator 8 wheels is about 50 wraps per inch. By reducing the wrap density of the matrix wheel 9 to about 30 wraps per inch, the air flow through the wheel can be increased substantially, for a given pressure drop across the wheel, with a relatively small loss 11 in system efficiency. On the other hand, an increase in the wrap density, with a 12 consequential reduction in air flow for a given pressure drop across the wheel, can be 13 achieved by winding the matrix strip materials more tightly. As examples, a 14 regenerator ventilation system nominally specified to deliver between 1000 and 1500 cubic feet per minute (CFM) of air can be modified according to the invention with 16 interchangeable matrix wheel sections to deliver up to approximately 2300 CFM of 17 air, an increase in performance of about 50%. Similarly, a system designed to deliver 18 up to 3000 CFM of air can be modified according to the invention to deliver up to 19 approximately 4500 CFM of air. This substantial increase in performance is obtained with only about a 10% loss in efficiency.

21 Thus, a rotary heat regenerator has been described with a regenerator matrix 22 comprising a plurality of individual segments of different performance characteristics, 23 the segments being easily exchangeable so as to adjust the performance characteristics 24 to meet the requirements at the site. It is clearly easier to tailor a ventilation system to specific requirements by adjusting relatively small components, such as by changing 26 heat transfer segments, than by adjusting large components, such as by changing the 27 entire wheel.

28 Thus, by utilizing certain segments made from a matrix of sensible heat 29 exchange material, and other segments made from a matrix of latent heat exchange 30 material, the present rotary heat regenerator is able to transfer latent heat with 31 efficiencies between those of regenerators comprising matrices made of only sensible WO 98/1 1 2 3 4 6 7 8 9 11 12 13 14 16 17 18 19 21 22 23 9763 PCTfUS97/20333 heat exchange material, and those regenerators made with only latent heat exchange materials. Through division of the matrix into removable elements together containing a selected combination of latent heat exchange material and sensible heat exchange material, the present rotary heat regenerator is further able to transfer latent heat with efficiencies which can be adjusted at the site of installation.

Furthermore, by providing segments of different surface area densities at the location of installation, the airflow versus efficiency and pressure drop performance characteristics of the regenerator can be adjusted and tailored to meet the requirements of the particular application. For example, if greater airflow is required through the wheel and reduced efficiency is acceptable, a wheel composed of matrix segments having a lower surface area density (greater spacing between adjacent strips in the matrix) can be selected. On the other hand, if greater efficiency is required and either reduced airflow or a greater pressure drop across the wheel is acceptable, then a wheel (or one or more matrix sections) having greater surface area density (closer spacing between adjacent strips in the matrix) can be selected at the site of installation. It should be appreciated that segments of different surface area densities can be combined in one regenerator to provide an average air flow rate through; or pressure drop across, the wheel.

In this disclosure, there are shown and described various preferred embodiments of the invention, but as aforementioned, it is to be understood that the invention is capable of use in various other conditions and environments and is capable of changes or modifications within the scope of the inventive concept as expressed herein.

Claims (22)

16- THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:- 1. A method of constructing a matrix wheel for use in an air transfer system and having at least one performance characteristic whose value is field adjustable as a function of the conditions at the location of installation, the method comprising: selecting a desired value for the performance characteristic as a function of the conditions at the location of installation; selecting individual segments from selectively interchangeable segments so that when the selected segments are combined as a wheel and the wheel is used, the wheel provides approximately said desired value of the field adjustable performance •characteristic; and arranging the selected ones of said individual segments so as to form the matrix of said wheel having the approximated desired value of the field adjustable performance characteristic. 2. A method according to claim 1, wherein the field adjustable characteristic is air flow as a function of the pressure drop across said wheel. 3. A method according to claim 1, wherein the field adjustable characteristic is the S 20 ratio of latent heat exchange efficiency to sensible heat exchange efficiency. *o 4. A method according to claim 1, wherein the field adjustable characteristic is the surface area density of the wheel, wherein the step of selecting individual wheel segments includes the steps of selecting from segments of differing surface area densities. A method according to claim 1, wherein the adjustable field characteristic is the ratio of latent heat exchange efficiency to sensible heat exchange efficiency, wherein the step of selecting individual segments includes the step of selecting from segments of differing ratios. P:\OPER\RSH\52493-98 139.dow-I May. 2000 -17- 6. A regenerator heat exchange device having an energy transfer matrix comprising a plurality of segments, each of said segments being formed of at least one heat exchange material, wherein each of said segments has a specific value of a performance characteristic which is predetermined, and wherein each of said segments is separately removable and interchangeable with any other corresponding segment such that at least two of the segments of said matrix have different values of the performance characteristic resulting in the value of the performance characteristic of the matrix being non-uniform throughout the matrix and adjustable following manufacture of the device by selectively interchanging at least one of the segments of one value of the performance characteristic with a corresponding segment of at least one other value of the performance characteristic. 7. A device according to claim 1, wherein the performance characteristic is the latent o. **heat exchange efficiency. 8. A device according to claim 6, wherein one of said at least two segments includes a o heat exchange surface made of latent heat exchange material, and the other of said at least two segments includes a heat exchange surface made of a sensible heat exchange material so that the ratio of the total surface area of latent heat exchange material and sensible heat exchange material of the matrix is adjustable by adjusting the ratio of the number of segments of said one segment to the number of segments of the other segment within said matrix so as to adjust the latent heat exchange efficiency of said matrix at the time of manufacture or installation or use. 9. A device according to claim 8, wherein said sensible heat exchange material is selected from the group consisting of a plastic, paper or aluminum material, and said latent heat exchange material is selected from the group consisting of a plastic, paper or aluminum material coated with a desiccant material. 10. A device according to claim 6, wherein the performance characteristic is the Ssurface area density of the matrix. P:\OPERRSH\52493-98 qp I39,dom-i May, 2000 -18- 11. A device according to claim 10, wherein each of said segments comprises a plurality of strips, and means for spacing each of the strips relative to one another so as to allow air to pass through said strips. 12. A device according to claim 11, wherein the means for spacing each of the strips relative to one another includes a plurality of alternating flat and distributed embossed strips. 13. A device according to claim 12, wherein each of said distributed embossed strips includes a plurality of distributed embossments, the height of the distributed embossments determining the spacing between adjacent flat strips, and wherein the height of the distributed embossments of the two segments are different so as to provide different .99 surface area densities. 14. A device according to claim 10, wherein one of said at least two segments includes a latent heat exchange material and the other of said two segments includes a sensible heat exchange material. o A device according to claim 14, wherein each of said removable segments 20 comprises a plurality of strips spaced from one another. soo• *9 16. A device according to claim 15, further including means for spacing said strips from one another.

17. A device according to claim 16, wherein the means for spacing the strips from one another includes embossments formed in at least one surface of alternate ones of said strips.

18. A device according to claim 17, wherein said sensible heat exchange material comprises plastic and said latent heat exchange material comprises plastic coated with a desiccant material. P:\OPER\RSM52493-98 Spe 139.dow-18 May. 2000

19- 19. A device according to claim 6, wherein said matrix contained within a wheel and said removable segments are wedge-shaped. In a ventilation system including a heat exchange device, the heat exchange device including amatrix comprising a plurality of segments, each of said segments being formed of at least one heat exchange material, wherein each of said segments has a predetermined value of a performance characteristic, and said segments are separately removable and interchangeable such that at least two of the segments of the matrix have different values of the performance characteristic resulting in the value of the performance characteristic being non-uniform throughout the matrix and adjustable following manufacture of the device by selectively interchanging at least one of the segments of one value of the performance characteristic with a corresponding segment of at least one other value of the performance characteristic. C C

21. A system according to claim 20, wherein the performance characteristic is the latent heat exchange efficiency. C S22. A system according to claim 20, wherein one of said at least two segments includes a heat exchange surface made of latent heat exchange material, and the other of 20 said at least two segments includes a heat exchange surface made of a sensible heat exchange material so that the ratio of the surface area of latent heat exchange material and sensible heat exchange material of the total matrix is adjustable by adjusting the ratio of the number of segments of said one interchangeable segment to the number of segments of the other interchangeable segment within said matrix so as to adjust the latent heat exchange efficiency of said matrix at the time of manufacture or installation or after use.

23. A system according to claim 22, wherein said sensible heat exchange material is selected from the group consisting of a plastic, paper or aluminum material, and said latent heat exchange material is selected from a plastic, paper or aluminum material coated with a 0 desiccant material. PAOPER\RSH\52493-98 s. 139.doc-18 May, 2000

24. A system according to claim 20, wherein the performance characteristic is the surface area density of the matrix. A system according to claim 24, wherein each of said segments comprises a plurality of strips, and means for spacing each of the strips relative to one another so as to allow air to pass through said strips.

26. A system according to claim 25, wherein the means for spacing each of the strips relative to one another includes a plurality of alternating flat and distributed embossed strips. 0o°

27. A system according to claim 26, wherein each of said distributed embossed strips includes a plurality of distributed embossments, the height of the distributed embossments determining the spacing between adjacent flat strips, and wherein the height of the 15 distributed embossments of at least one of the one segments is different from the height of the distributed embossments of at least one other of the segments so as to provide different **surface area densities.

28. A system according to claim 24, wherein one of said at least two segments includes a latent heat exchange material and the other of said two segments includes a sensible heat exchange material.

29. A system according to claim 28, wherein each of said removable segments comprises a plurality of strips spaced from one another. A system according to claim 29, further including means for spacing said strips from one another.

31. A system according to claim 30, wherein the means for spacing the strips from one another includes embossments formed in at least one surface of alternate ones of said strips. P:\OPERRSW\2493-98 Spe 139.doc1 May, 2000 -21-

32. A system according to claim 31, wherein said sensible heat exchange material includes a material selected from the group consisting of a plastic, paper or aluminum material, and said latent heat exchange material includes a material selected from the group consisting of plastic, paper or aluminum material coated with a desiccant material.

33. A system according to claim 20, wherein said matrix segment are contained within a wheel and said removable segments are wedge-shaped.

34. A regenerator heat exchange system comprising a wheel comprising a matrix V0 00 10 including a plurality of removable individual heat exchange segments at least two of which differ in construction so as to exhibit different values of at least one performance 0* 0 characteristic, wherein the segments of said matrix are easily arranged so that a desired 600 000:• •value of the performance characteristic of said wheel can be approximated at the location 0 of manufacture or installation by substituting one segment of one construction with a 15 corresponding segment of a different construction. woo* 0 A regenerator heat exchange system according to claim 34, wherein said S. performance characteristics include one or more of the following: latent heat exchange efficiency, sensible heat exchange efficiency, overall system efficiency, volumetric airflow rate and pressure drop.

36. A regenerator heat exchange system according to claim 34, wherein at least one of said segments includes latent heat exchange material and at least one includes sensible heat exchange material, each material providing a determinable surface area exposed to air flowing through the matrix, wherein the relative proportion of each material within the matrix is adjustable at the location of installation by adjusting the number of said first and second segments used for said matrix.

37. A regenerator heat exchange system according to claim 36, wherein said each Csegment of said matrix includes a plurality of strips stacked so as to form a matrix Zsegment. P:\OPER\RSH32493-98 spe 139.doc-18 May, 2000 -22-

38. A regenerator heat exchange system according to claim 37, further including means for spacing each of the strips relative to one another so as to allow air to pass through said strips.

39. A regenerator heat exchange system according to claim 38, wherein at least some of said strips includes a latent heat exchange material. A regenerator heat exchange system according to claim 38, wherein at least some of said strips includes a sensible heat exchange material.

41. A regenerator heat exchange system according to claim 38, wherein the means for 0 spacing each of the strips relative to one another includes a plurality of distributed embossments in at least every other strip. 15 42. A regenerator heat exchange system according to claim 41, wherein the dimensions of said embossments are preselected to provide a desired spacing between adjacent strips, thereby establishing a desired surface area density of each of said strips within said matrix, and wherein the dimensions of said embossments of at least two of the segments are different. foe:

43. A regenerator heat exchange system according to claim 36, wherein said sensible heat exchange material is selected from the group consisting of a plastic, paper or aluminum material and said latent heat exchange material is selected from a group consisting of a plastic, paper or aluminum material coated with a desiccant material.

44. A regenerator heat exchange system according to claim 34, wherein said selectively removable segments are designed to provide two or more surface area densities. P:\OPER\RSH\32493-96 p 139.do-I8 My, 2000 23 A regenerator heat exchange system according to claim 44, wherein at least one of said removable elements includes a latent heat exchange material and at least one other of said removable elements includes a sensible heat exchange material. DATED this 2 2 nd day of May, 2000 AirXchange, Inc. By its Patent Attorneys: DAVIES COLLISON CAVE